I've been in a four-year debate with myself around whether our marketing emails should be mainly "pretty" HTML that reinforce our brand, and plain text emails that appear to come from a person.
Here's where I've settled:
1) Our weekly thought-leadership centered content campaigns come from our brand (Corporate Visions), look pretty, and can have formatted text.
2) Nurturing emails (when we're trying to draw a lead into a sales cycle) come from a specific person (lead owner) and are plain text with a video image link (found that to be a best practice).
3) Small-group event invitations are plain text, similar to #2.
4) Large-group conference events are fancy, from the brand, look pretty and showcase the "theme" of the event.
I've noticed that plain text emails tend to have around 0.3% of so higher click-rates, but... I feel like I'm willing to sacrifice that for developing a bit of brand recognition. I've noticed that Marketo doesn't shy away from sending emails from their brand and with a splash of purple.
What are other folks out there doing?